Database Fundamentals Q&A

Q: What are the fundamentals of databases interviewers expect you to know? A: Core areas typically probed: ACID properties (Atomicity, Consistency, Isolation, Durability) and what each guarantees; normalization forms (1NF-3NF) and when denormalization is a valid tradeoff; indexing (B-Tree vs Hash indexes) and how they speed up reads at the cost of writes/storage; transaction isolation levels (Read Uncommitted through Serializable) and the anomalies each prevents (dirty reads, non-repeatable reads, phantom reads); the difference between clustered and non-clustered indexes; and basic query optimization (how an execution plan/EXPLAIN works). Be ready to reason about trade-offs rather than just recite definitions.